WWP2 promotes degradation of transcription factor OCT4 in human embryonic stem cells  

作　　者：Huiming Xu Weicheng Wang Chunliang Li Hongyao Yu Acong Yang Beibei Wang Ying Jin 

机构地区：[1]Shanghai Stem Cell Institute, Shanghai Jiao Tong University School of Medicine, 225 South Chongqing Road, Shanghai 200025, China [2]Key Laboratory of Stem Cell Biology, Institute of Health Sciences, Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences/Shanghai Jiao Tong University School of Medicine, Shanghai 200031, China [3]Key Laboratory of Cell Differ- entiation and Apoptosis of Chinese Ministry of Education, Shanghai Jiao Tong University School of Medicine, Shanghai 200025, China

出　　处：《Cell Research》2009年第5期561-573,共13页细胞研究（英文版）

基　　金：Acknowledgments We are grateful to Dr DA Melton （Harvard University） for shar- ing his human ES cells with us. The study was supported by grants from the National High Technology Research and Development Program of China （2006CB943900）, the National Natural Science Foundation of China （General Program, 30500088）, the Shang- hai Jiao Tong University School of Medicine, and the Shanghai Institutes for Biological Sciences, Chinese Academy of Sciences. The study was also supported by the Shanghai Leading Academic Deciline Project （S30201）.

摘　　要：POU transcription factor OCT4 not only plays an essential role in maintaining the pluripotent and self-renewing state of embryonic stem （ES） cells but also acts as a cell fate determinant through a gene dosage effect. However, the molecular mechanisms that control the intracellular OCT4 protein level remain elusive. Here, we report that human WWP2, an E3 ubiquitin （Ub）-protein ligase, interacts with OCT4 specifically through its WW domain and enhances Ub modification of OCT4 both in vitro and in vivo. We first demonstrated that endogenous OCT4 in hu- man ES cells can be post-translationally modified by Ub. Furthermore, we found that WWP2 promoted degradation of OCT4 through the 26S proteasome in a dosage-dependent manner, and the active site cysteine residue of WWP2 was required for both its enzymatic activity and proteolytic effect on OCT4. Remarkably, our data show that the en- dogenous OCT4 protein level was significantly elevated when WWP2 expression was downregulated by specific RNA interference （RNAi）, suggesting that WWP2 is an important regulator for maintaining a proper OCT4 protein level in human ES cells. Moreover, northern blot analysis showed that the WWP2 transcript was widely present in diverse human tissues/organs and highly expressed in undifferentiated human ES cells. However, its expression level was quickly decreased after human ES cells differentiated, indicating that WWP2 expression might be developmentally regulated. Our findings demonstrate that WWP2 is an important regulator of the OCT4 protein level in human ES cells.

关 键 词：transcription factor OCT4 WWP2 protein degradation embryonic stem cells 

分 类 号：Q813[生物学—生物工程] Q753